1. Field of the Invention
The present invention is directed to controlling network transmissions. More particularly, the present invention relates to scheduling transmissions from multiple clients in a network environment.
2. Background Art
With the advent of the Internet, it has become more commonplace to develop vast communications networks to readily exchange information over remote areas. As modern technology continues to evolve to create new services to be provided over communications media, a greater demand has been generated for bandwidth and improved quality of services. For example, television broadcasts historically involved one-way communication from a broadcast transmitter to a viewer's home. As interactive or personal television services continue to grow, communications media used to support one-way communications must now contend with an increased demand for bi-directional communications.
In a conventional communications network, a communications device (such as a modem) would request bandwidth from a headend prior to transmitting data to its destination. The headend would allocate bandwidth to the cable modem based on availability and competing demands from other modems. The allocation of bandwidth is typically granted to the requesting modem in a MAP. The cable modem would be required to follow the instructions specified in the MAP, and use the grant for the service specified in the MAP.
Problems arise when the service specified in the MAP is later determined to no longer require the bandwidth, or require more bandwidth than originally requested. Another problem can occur if another service of equal or higher priority should require immediate bandwidth shortly after the headend's granting a lower-priority service's request bandwidth. The cable modem may not be able to use the granted bandwidth to transmit data from the higher priority service, because the grant would be restricted to the lower priority service. For example, a DOCSIS-compliant network system specifies that a cable modem must accept decisions made during the requesting phase.
One mechanism that can be implemented to reduce latency would be to utilize piggyback requests for bandwidth. Piggyback requests can be very effective if a cable modem is operating in a contention mode, where the modem transmit packets without a specified grant. Transmitting a signal during a contention mode increases the likelihood of the packets colliding, getting loss or becoming corrupted.
However, the conventional way of piggybacking requests is to use variable sized headers. The header can be extended to incorporate the piggyback request when there exist a need to send one. This is a common practice in a DOCSIS-compliant environment. This approach is more effective if the header is very small and/or the size of the request message is also small. Otherwise, piggybacking requests can add excessive packet overhead that require more bandwidth or may cause packet latency.
Consequently, a system and method are needed to solve the above-identified problems and provide a simple, efficient and cost-effective way to schedule communications in an classify packets in a dynamic environment.